Dipole γ-ray transition rates in 238U

M1 and E1 transition rates from the ground to excited states and between excited states in ²³⁸U are calculated within the quasiparticle-phonon nuclear model with the wave functions consisting of one- and two-phonon terms. We show that there are relatively large M1 transitions between 2⁺ states in the low-energy region. The fragmentation of the one-phonon states strongly affects M1 and E1 strength distributions. The correlation takes place between E1 and E3 transition strengths. We show that there are fast E1 and M1 transitions between large components of the wave functions differing by an octupole or quadrupole phonon.     

Correlation effects of two interacting particles in a circular billiard

The maximal Lyapunov exponent is determined numerically for two classical unequal-mass interacting particles inside a circular billiard and subjected to a static magnetic field. A Yukawa potential is used for the interaction between the particles. Transitions from short to long interaction ranges and from equal to infinite mass ratio between particles are discussed. Correlations effects between particles strongly determine the dynamics inside the billiard. A qualitative change in the Lyapunov exponent dependence on the interaction range between particles is observed by the transition from weak to strong couplings. Poincaré surfaces of section are also used to describe the dynamics in the limit of infinite mass ratio.     

Near approach of two conducting spheres: Enhancement of external electric field

An external electric field applied to two uncharged conducting spheres in close approach is amplified (by charge separation on the spheres) in the region between the spheres. This enhancement increases without limit as the separation between the spheres decreases. We calculate the enhancement factor analytically, for spheres of radii a and b. A compact formula is given for the case where the separation s between the spheres is small compared to both a and b.     

Room temperature ferromagnetism in Cu–Gd co-doped GaN nanowires: A first-principles study

The electronic structure and room temperature ferromagnetism of wurtzite Cu–Gd co-doped GaN nanowires have been investigated by means of the first-principles calculations within the density functional theory, including the on-site Coulomb energy U. The magnetic coupling between Gd atoms in the Gd-doped GaN nanowire is paramagnetic instead of ferromagnetic (FM) as in the bulk structure. After replacing Ga with Cu atom we find a stable FM coupling between Gd magnetic moments in this p-type system. p–d coupling between Cu-3d and N-2p states pushes N-2p states up to Fermi level due to the existence of hole states introduced by Cu dopants. While the p–d coupling between host N-2p and Gd-5d states near Fermi level stabilizes a FM phase of Gd magnetic moments. Furthermore, we get a FM state above room temperature by increasing the holes concentration.     

Phase differences between quantum oscillations of the magnetoresistance and the hall effect in Hg1−xMnxTe and Hg1−xCdxTe

A Landau-level broadening-dependent phase shift has been observed between the Shubnikovde Haas oscillations of the magnetoresistance and the Hall effect in a series of Hg_1−xMn_xTe and Hg_1−xCd_xTe samples. The phase shift varies between 0 and 90° and appears not to be influenced by the exchange interaction between the Mn²⁺ ions and the carriers. The results are in good agreement with the theoretical predictions for short range scattering potentials.     

Particle correlations in e + e − → W + W − events

Preliminary results are reported on the two-particle correlation function R(Q) in hadronic Z decays, fully hadronic WW decays, and mixed hadronic-leptonic WW decays using data collected by the DELPHI detector at LEP at energies between 189 and 206 GeV. Evidence for Bose-Einstein correlations was observed in all three cases. The event mixing technique was used to determine correlations between particles arisingfrom different W bosons in fully hadronic WW decays. An excess of like-sign particle pairs with low four-momentum difference in fully hadronic WW events is observed, consistent with the effect expected from correlations between identical particles from different W bosons.     

The effect of electron-hole scattering on transport properties of a 2D semimetal in the HgTe quantum well

The influence of e-h scattering on the conductivity and magnetotransport of 2D semimetallic HgTe is studied both theoretically and experimentally. The presence of e-h scattering leads to the friction between electrons and holes resulting in a large temperature-dependent contribution to the transport coefficients. The coefficient of friction between electrons and holes is determined. The comparison of experimental data with the theory shows that the interaction between electrons and holes based on the long-range Coulomb potential strongly underestimates the e-h friction. The experimental results are in agreement with the model of strong short-range e-h interaction.     

Energy dependence of σp-air up to 20 TeV

The observed neutral to charge ratio in unaccompanied atmospheric hadron fluxes is used to improve the cosmic ray lower bound on the p-air inelastic cross section between 0.5 and 20 TeV. The conclusion drawn about the magnitude of continued increase of σ_pp between 2 and 20 TeV depends on the model relation between σ_pp and σ_p-air.     

The factors contributing to the band gap bowing of the dilute nitride GaNP alloy

The factors contributing to the band gap bowing of the dilute nitride GaNP are analyzed. It is found that the band gap bowing is due to two factors. One is the coupling interaction between the N level and the Γ conduction band minimum of GaP. The other is the coupling interaction between the N level and the X conduction band minimum of GaP. We also estimate the band gap reduction due to each factor. It is found that the band gap bowing is mainly due to the coupling interaction between the N level and the Γ conduction band minimum of GaP.     

The influence of interatomic distances on magnetic ordering in RMnSi compounds (R=La, Y, Sm, and Gd)

Magnetic ordering in the RMnSi (R=La, Y, Sm, and Gd) compounds is investigated. It is found that the type of magnetic ordering depends on the d _Mn-Mn distance between manganese atoms inside the magnetic layers located in the planes perpendicular to the c axis. This inference is based on the results of studies performed with SmMnSi and GdMnSi compounds in which the distances between manganese atoms are close to the critical value d _Mn-Mn that corresponds to the crossover between ferromagnetic and antiferromagnetic ordering in RMnSi compounds. The introduction of lanthanum and yttrium atoms into the rare-earth sublattice leads to an increase and a decrease in the unit cell size, respectively, and brings about magnetic phase transitions in the compounds under investigation.     

Time-dependent mean field S-matrix theory

By using the path integral approach to many-body systems, we formulate a time-dependent mean field S-matrix theory of nuclear reactions. Many-body channel eigenstates are constructed by using projection techniques. In this way the S-matrix between the channel eigenstates is expressed as a superposition of S-matrix elements between wave-packet-like states localized in space and time. A field operator representation of the interaction picture S-matrix is derived which enables one to apply the path integral approach. Applying the stationary phase approximation to the path integral representation of the interaction picture S-matrix between the localized states an asymptotically constant time-dependent mean field approximation to this S-matrix is obtained. Finally, the S-matrix between the projected channel eigenstates is obtained by evaluating the integral, arising from the projections, over the space-time positions of the localized states in the stationary phase approximation. The stationary phase conditions select those localized states from the projected channel states for which the mean field values of energy and momentum coincide with their corresponding channel eigenvalues.     

Effects of atomic-scale contacts on transport properties through single molecules - ab initio study

Using the RTM/NEGF method, which is a first-principles calculation tool for the quantum transport through nanostructures between electrodes, we study the effects of atomic-scale contacts on the transport properties through single molecules. Electronic states and current-voltage (I-V) characteristics are investigated in various contact conditions with and without single molecules between electrodes. We find that similar nonlinear behaviors appear in the I-V characteristics. Such nonlinear behaviors are determined not only by the HOMO-LUMO electronic states of single molecules between electrodes, but also by the atomic-scale contact conditions. We show that the transitions from tunneling to ballistic regimes affect the I-V characteristics significantly.     

Low-lying excitations in the S = 1 antiferromagnetic Heisenberg chain

In order to confirm the picture of domain-wall excitations in the hidden antiferromagnetic order of the Haldane phase, the structure of the low-lying excitations in the S = 1 antiferromagnetic Heisenberg chain is studied by a quantum Monte Carlo method. It is confirmed that there exists a finite energy gap between the first- and the second-excited states at k = π as well as between the ground state and the first-excited state at k = π. In the thermodynamic limit, the second-excited state at k = π is separated from the ground state by the gap which is three times as large as the Haldane gap. From the size dependences of the low-lying-excitation energies, the interactions between the elementary excitations in the excited states are concluded to be repulsive.     

Percolation on bipartite scale-free networks

Recent studies introduced biased (degree-dependent) edge percolation as a model for failures in real-life systems. In this work, such process is applied to networks consisting of two types of nodes with edges running only between nodes of unlike type. Such bipartite graphs appear in many social networks, for instance in affiliation networks and in sexual-contact networks in which both types of nodes show the scale-free characteristic for the degree distribution. During the depreciation process, an edge between nodes with degrees k and q is retained with a probability proportional to (kq)^−α, where α is positive so that links between hubs are more prone to failure. The removal process is studied analytically by introducing a generating functions theory. We deduce exact self-consistent equations describing the system at a macroscopic level and discuss the percolation transition. Critical exponents are obtained by exploiting the Fortuin-Kasteleyn construction which provides a link between our model and a limit of the Potts model.     

The analyzing power Ay(θ) for the 9Be(p, n)9B reaction from 8 TO 15 MeV

The analyzing power A_y(θ) for the ⁹Be(p, n)⁹B reaction was measured at seven energies between 8.1 to 15.0 MeV for reaction angles between 0° and 100° (c.m.). The A_y(θ) values are predominantly negative and exhibit a smooth variation with energy. The significance of these results in Lane optical- model calculations for the ⁹Be + nucleon system and in comparisons between the observables P^y(θ) and A_y(θ) is indicated.     

Josephson effect in supercondutor/ferromagnetic semiconductor/superconductor junctions

Using a general expression for dc Josephson current, we study the Josephson effect in ballistic superconductor (SC)/ferromagnetic semiconductor (FS)/SC junctions, in which the mismatches of the effective mass and Fermi velocity between the FS and SC, spin polarization P in the FS, as well as strengths of potential scattering Z at the interfaces are included. It is shown that in the coherent regime, the oscillatory dependences of the maximum Josephson current on the FS layer thickness L and Josephson current on the macroscopic phase difference φ for the heavy and light holes, resulting from the spin splitting energy gained or lost by a quasiparticle Andreev-reflected at the FS/SC interface, are much different due to the different mismatches in the effective mass and Fermi velocity between the FS and the SC, which is related to the crossovers between positive (0) and negative (π) couplings or equivalently 0 and π junctions. Also, we find that, for the same reason, Z and P are required not to surpass different critical values for the Josephson currents of the heavy and light holes. Furthermore, it is found that, for the dependence of the Josephson current on φ, regardless of how L,Z, and P change, the Josephson junctions do not transit between 0 and π junctions for the light hole.     

Regulation of Entanglement and Geometric Quantum Discord of Hybrid Superconducting Qubits for Circuit QED

We investigate the dynamic evolution behaviors of entanglement and geometric quantum discord (GQD) of hybrid qubits in a circuit QED system. Under certain initial conditions, interactions between qubits and that between the qubit and the cavity can suppress the decay of entanglement and GQD of qubits. Under the initial condition |ψ _Q (0)〉 _I =sinα|↓↑〉+cosα|↑↓〉, such decay was avoided by increasing the coupling strength ratio between qubits and that between the qubit and the cavity. Under the aforementioned condition, the survival time of entanglement and GQD was prolonged by decreasing the coupling strength ratio between qubits and that between the qubit and the cavity.     

Allowed and forbiddenn=2-2 transitions of highly ionised titanium

Relativistic intermediate-coupling wavefunctions are used to evaluate transition energies, line strengths and transition probabilities for all allowed and forbiddenn=2-2 transitions for beryllium-like titanium ion. We have shown that to achieve a better than 1% agreement between theory and experiment for transition energies between then=2-2 levels it is not sufficient to use the three-configuration basis composed of 2s ², 2s2p and 2p ².     

Associations of Speaking-Voice Parameters With Personality and Behavior in School-Aged Children

ObjectivesPrevious studies suggest a link between voice disorders and personality traits. However, nearly nothing is known about the relationship between personality and voice parameters in healthy children. The present study investigated associations between children's personality and the intensity and frequency of their speaking voice.Study DesignThis is a cross-sectional analysis.MethodsThe study participants included 871 German children aged from 7 to 14 who had not yet experienced voice change in puberty. Within the framework of the LIFE Child study, all participants were asked to perform a speaking-voice task at four different intensity levels (quietest, conversational, presentation, and shouting voice). Associations of fundamental frequency and voice intensity with children's personality and behavioral strengths and difficulties (assessed using parent-reported questionnaires) were estimated using multiple linear regression analyses.ResultsWith respect to children's personality, the analyses revealed significant positive associations between speaking-voice intensity and extraversion (eg, for the conversational voice, β = 0.16, P < 0.001) as well as significant negative associations between voice intensity and emotional stability (eg, for the shouting voice, β = −0.15, P = 0.004) and conscientiousness (for the shouting voice, β = −0.10, P = 0.033). Regarding behavioral strengths and difficulties, we observed significant positive associations between voice intensity and peer-relationship problems (eg, for the conversational voice, β = 0.14, P = 0.001) and prosocial behavior (for the conversational voice, β = 0.11, P = 0.015). In contrast, no significant association was found between speaking fundamental frequency and personality or behavioral difficulties/strengths.ConclusionsIn children, associations exist between a child's speaking-voice intensity and his or her personality, especially extraversion and emotional stability, and behavioral characteristics.     

Composition dependence of optical and electrical characteristics in flash evaporated Pb1−xHgxTe films

Structural, optical and electrical analyses of flash evaporated lead-mercury telluride films indicate that under appropriate conditions of growth ternary Pb_1−xHg_xTe compounds are formed in the single phase crystalline films. Optical band gaps of the crystalline films, grown on substrates at temperatures (Ts) of 25 and 100°C, are observed to decrease with increase in mercury concentration in the films. The optical gap decreases between 0.27 and 0.14 eV in the 0.07 ⩽x⩽ 0.50 Ts of 25°C films and between 0.23 and 0.09 eV in the Ts of 100°C 0.07 ⩽x⩽ 0.93 films. Activation energy values, calculated from electrical conductivity measurements, indicate that between 350 and 500 K, the conduction is mainly due to thermally generated charge carriers, whereas impurity conduction dominates at temperatures <250K. All crystalline films are observed to be photoconducting.